exercise and the cardiovascular system - eiucfje/4340/4340-cv2.pdf · ¥ during exercise the o2...
TRANSCRIPT
Exercise and the Cardiovascular System
Oxygen Supply
• T h e F i c k E q u a t i o n
• VO2 = Q x a-v O2 difference
• or
• VO2 = HR x SV x a-v O2 difference
Supply and Demand
• Example...at rest the muscles demand (or need) 0.21 Liters of O2/min...
• demand is met with a supply of = 60 beats/min x 70 ml/beat x 5 ml O2/100 ml blood
• = 4,200 ml/min x 5 ml of O2 / 100 ml of blood
• = 42 ml/min x 5 ml of O2
• = 210 ml of O2/min
• = 0.21 Liters of O2/min
Supply and Demand• Example...during exercise the muscles need 2.496
Liters of O2/min...
• Then, the demand is met with a supply of... = 160 beats/min x 130 ml/beat x 12 ml O2/100 ml blood
• = 20,800 ml/min x 12 ml of O2 / 100 ml of blood
• = 208 ml/min x 12 ml of O2
• = 2,496 ml of O2/min
• = 2.496 Liters of O2/min
Supply and Demand
• During exercise the O2 demand of the muscles increase
• Therefore the CV systems needs to increase O2 supply
• The next series of slides will answer how this is accomplished.
SUBMAXIMAL EXERCISE
• Steady state, continuous exercise
Cardiac Output & Exercise
• Q = HR x SV
• Represents the amount of blood flow to the musclesSubmaximal Exercise
Heart Rate & Exercise
• Sympathetic nervous system
• Parasympathetic nervous system
• Catecholamines released
Submaximal Exercise
Stroke Volume & Exercise
1. ↑ Preload (or end-diastolic volume)
• Muscle pump
• Venoconstriction
2. ↑ Strength of contraction
• Sympathetic stimulation
3. ↓ Afterload
• VasodilationSubmaximal Exercise
Venoconstriction
Muscle PumpIncrease Preload
or blood flow into the heart
Preload
Afterload
Vasodilation
Decrease afterload leading to increase blood flow out of the heart
Vasodilation
Autoregulation or Metabolic Vasodilation
• Waste products from muscle contraction.
• ↑ CO2 and ↑ acid
• Other
• ↑ potassium, ↑ adenosine, and ↑ nitric oxide
a-v O2 Difference & Exercise
• At rest: 5 ml of O2/100 ml of blood
• Increase during exercise
• ↓ partial pressure
• redistribution of blood flow
Submaximal Exercise
Partial Pressure
The total pressure of a gas = sum of the partial pressures of each gas
Example: partial pressure of oxygen (PO2)• Air is 20.93% oxygen• Expressed as a fraction: 0.2093• Total pressure of air = 760 mmHg
PO2 = 0.2093 x 760 = 159 mmHg
Partial Pressure
Partial Pressure and a-v O2 difference
Rest
PO2 = 40
PO2 = 100
PO2 = 100
PO2 = 100
no movement of O2
Submaximal Exercise
Exercise
PO2 = 15
PO2 = 100
Redistribution of Blood FlowVASOCONSTRICTION
VASODILATION
Submaximal Exercise
Redistribution of Blood Flow During Exercise
VASOCONSTRICTION
VASODILATION
O2 Supply Summary
• How is the increase in O2 demand by the muscles during exercise met?
• Increase Q
• Increase HR
• Increase SV
• Increase a-v O2 difference
Blood Pressure
Upper Body Exercise
PROLONGED, SUBMAXIMAL EXERCISE
Cardiovascular Drift
Heart Rate
Cardiac Output
Stroke Volume
Steady State, Submaximal Exercise
INCREMENTAL EXERCISE TO MAXIMAL EFFORT
SPEED
ELEVATION
Circ
ulat
ory
Resp
onse
s to
Incr
emen
tal E
xerc
ise
Incremental Exercise
Circulatory Responses to Incremental Exercise
Cardiac Output Heart Rate
Incremental Exercise
Maximum Heart Rate
• HRmax = 220 – age is an estimation, only
• Margin of error ± 12 bpm
• ALTERNATIVE FORMULA
• HRmax = 208 – (0.70 x age)
F.Y.I.
Incremental Exercise
Circulatory Responses to Incremental Exercise
• Stroke Volume
Incremental Exercise
Circulatory Responses to Incremental Exercise
• Systolic blood pressure
• Diastolic blood pressure
Incremental Exercise
Cardiac Output
Heart Rate
Stroke VolumeNote the plateau
Endurance Training
Pages 264-270
Heart rateAt rest
Increase parasympathetic stimulationIncrease in SV
During steady state exerciseAt maximal exercise
Adaptations from Chronic Exercise
Adaptations from Chronic Exercise
Stroke Volume
At rest
Steady state exercise
Maximal exercise
Cardiac Output
At rest
Steady state exercise
Maximal exercise
Adaptations from Chronic Exercise
a-v O2 difference
At rest
During steady state exercise
At maximal exercise
Adaptations from Chronic Exercise
Oxygen Uptake (VO2)
At rest
Submaximal exercise
Maximal exercise (VO2max) by 25-30%
Genetics: 40-66% of baseline VO2max
Improvements in VO2max
50% due to ↑ SV
50% due to ↑ a-vO2
Adaptations from Chronic Exercise
Blood
Total blood volume
Plasma volume
Red blood cells
Hematocrit
Adaptations from Chronic Exercise
Blood Pressure (p. 333)
What is hypertension?
What affect does chronic exercise training have on hypertension?
Adaptations from Chronic Exercise
Overview
↓Blood PressureBlood volume
Heart sizeHeart strength
Adaptations from Chronic Exercise
Rest Submax MaxQ ↔ ↔ ↑SVHR
a-vO2 diffPlasma vol
RBCHtBP
Detraining
Stroke Volume
(Blood Volume)
a-v O2 difference
RetrainingContinued
Retraining
Detraining
Detraining & Retraining
About 50% of the increase in mitochondria was lost after one week of detraining All of the adaptations were lost after five weeks of detrainingIt took four weeks of retraining to regain the adaptations lost in the first week of detraining